Tube Breather KZ650

I've got a quick question for those who are more knowledgeable than I.

I recently noticed that the tube breather (Part # 92059-137, #14, that goes from the air box to the top of the engine area) on my bike is barely attached at either end. I have a '78 kz650 that I just bought (10,000mi and keep discovering problems with )... it has the stock- airbox, so I'm assuming that this tube being exposed to open air is a no-no. The problem is that the tube is all chewed up, and it seems as though the airbox is not seated right because it has to bend really awkwardly for the ends of the tube to fit where they should go. I got it semi-attached, but its not sealed.

Just wondering what this tube actually was for, and how high I should prioritize this problem I'm hoping its just a breather and doesnt require fresh air...

Thanks for the help

That is the crankcase breather.
It lets the crankcase vent, to the air box.
Mine has a crack on one end, and is causing a bit of oilly residue to build further back on the bike.
You and I should address the problem, but it's not overly important.
I've been running like this for over a year.

Do check that the mounts #12 are attached, as you say your breather seems to not be fitting properly.

sft1662,

See PM. Ed

Thanks guys, I'll add it to the To-Do list. I'm glad that I can still ride without fixing it though

Crankcase vent may be routed to exit underneath bike to open air.

Avoids possibility of fuel in airbox draining on down through the S-tube connection jnto the crankcase and thereby contaminating the oil.

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Good Fortune!

Thanks Patton, looks like that might be a good way to go!

I threw a mini air filter meant for a car PCV on there look like a mini pod filter actually, the hose will work too .

The vacuum in the airbox draws on the breather tube helping crankcase ventilation. Any fuel that might somehow go from the carbs into the airbox will drain from the bottom airbox drain tube long before it would ever reach the breather tube which is located higher on the airbox. Ed

650ed wrote:

The vacuum in the airbox draws on the breather tube helping crankcase ventilation. Any fuel that might somehow go from the carbs into the airbox will drain from the bottom airbox drain tube long before it would ever reach the breather tube which is located higher on the airbox. Ed

Any fuel that might somehow go from the carbs into the airbox will drain from the bottom airbox drain tube long before it would ever reach the breather tube which is located higher on the airbox.

This may be true on some bikes, but not on Z1 with oem airbox. I wish it was.

And also assumes airbox drain is unclogged and actually functioning well enough to sufficiently discharge the incoming fuel before it reaches a level high enough to drain out and down the S-tube.

Needed to hear about this non-issue at 2 am in the 7-11 parking lot while draining the Z1's fuel-thinned crankcase oil and refilling after removing the oem S-shaped fitting. All of which happened during a ride, stopped for fuel, and noticed oil level way too high. Sniffed the oil, and guess what.

And Oh Yes, Thank God for needle bearings.

So this condition not only may result from leaving the petcock "ON" while bike is parked overnight, but also while riding, where the float valve is malfunctioning, or for any other reason excess fuel is getting past the float valve into the bowl and rising on up into the carb throat to flow into the airbox.

Of course with pods, the potential problem of fuel drainage through breather doesn't pose much of a risk. :lol:

But even with pods, excess fuel rising into the carb throat flows both directions, backward, and forward toward engine, where it may enter combustion chamber and flush down around pistons into the crankcase.

The potential engine damage resulting from fuel intrusion into the crankcase is so catastrophic that imo it's simply not worth the risk.

Good Fortune!

I guess Kawasaki had some lessons learned from the Z1 before they designed our KZ650 airboxes. Of course, excess fuel in the bowls should actually drain through the carb overflow tubes. These generally work very well (or at least one of mine did in my driveway when a float valve stuck, lucky I don't smoke)

650ed wrote:

I guess Kawasaki had some lessons learned from the Z1 before they designed our KZ650 airboxes. Of course, excess fuel in the bowls should actually drain through the carb overflow tubes. These generally work very well (or at least one of mine did in my driveway when a float valve stuck, lucky I don't smoke)

Yes, properly functioning carb overflow circuits go a long way toward avoiding the problem. However, some carbs, such as smoothbores, don't have overflow circuits.

And sometimes the overflow circuits get clogged, or the drain tubes get crimped or pinched or blocked. And the overflow circuits may be difficult to clean, or go unattended incident to carb rebuild.

Am still using the oem S-tube on KZ900, with oem manual slide Mikuni 26mm carbs, having overflow circuits.

And all the more reason, regardless of carb design, to use accessory in-line fuel filters, to keep grit and crud away from the float valves.

Good Fortune!

sft1662's posted question concerns KZ650's L -shaped tube from crankcase vent, which attaches to side (not bottom) of airbox.

I likely confused matters :blush: with info about other designs regarding similarly purposed S -shaped tube on Z1 and KZ900, which attaches to bottom (not side) of airbox.

With either design, the vent may be re-routed to exit underneath bike. However, as correctly noted by 650ed, such re-routing does eliminate airbox's beneficial vacuum pull from crankcase vent, and would seem less necessary with the L -shaped design attached higher on side (not bottom) of airbox.

Actually, the S -shaped tube on Z1 attaches to the airbox at a level significantly higher than the drain hole through bottom of the airbox. But the design never-the-less permits the unwanted fuel (or at least some of the unwanted fuel) flowing from carb throat into airbox to drain down through the S-shaped tube before getting to the airbox bottom drain hole.

Good Fortune!

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